Increased breast cancer risk in in vitro fertilisation treated women with a multiple pregnancy: a new hypothesis based on historical in vitro fertilisation treatment data.

BACKGROUND: Breast cancer risk is temporarily increased after a full-term pregnancy and declines thereafter, possibly due to increased levels of gonadal and placental hormones during pregnancy. Inconsistent results, however, have been reported after twin pregnancies with higher hormone levels. Among women treated with in vitro fertilisation (IVF), for whom the number of embryos available for implantation is known, we recently observed that a multiple birth after implantation of all transferred embryos is associated with higher levels of vascular endothelial growth factor (VEGF). As VEGF is involved in breast cancer progression, we studied the effects of embryo implantation and a multiple birth on breast cancer risk in a nationwide Dutch cohort of IVF-treated women. METHODS: We performed a cohort analysis among 12,589 women who had been treated with IVF between 1983 and 1995 and completed a risk factor questionnaire between 1997 and 1999. Data on IVF treatment were obtained from medical records. Breast cancer cases were ascertained through linkage with the population-based Netherlands Cancer Registry. Breast cancer risks associated with singleton and multiple births were estimated with Cox regression. FINDINGS: There were 1688 women (13.4%) with multiples, 6027 (47.9%) with singletons and 4874 (38.7%) nulliparous women. Breast cancer occurred in 317 women of whom 57 had multiples. Breast cancer risk was 1.44 times higher in mothers of multiples than in mothers of singletons (95% confidence interval (CI) 1.06-1.97). Risk was highest in women who gave birth to multiples from all embryos transferred (adjusted hazard ratio (HR) 1.86, 95% CI 1.01-3.43), and lower for those with multiples after incomplete embryo implantation (adjusted HR 1.31, 95% CI 0.76-2.25). INTERPRETATION: A woman's potential to implant all transferred embryos may be associated with breast cancer risk. Further research is needed to confirm our results and to identify the underlying biological mechanisms.

Preconceptional low-dose aspirin for the prevention of hypertensive pregnancy complications and preterm delivery after IVF: a meta-analysis with individual patient data.

STUDY QUESTION: Does preconceptionally started low-dose aspirin prevent hypertensive pregnancy complications and preterm delivery in IVF patients? SUMMARY ANSWER: The current data do not support the use of preconceptionally started low-dose aspirin treatment for the prevention of hypertensive pregnancy complications and preterm delivery in IVF women. WHAT IS KNOWN ALREADY: Studies starting low-dose aspirin treatment as prevention in the second trimester of pregnancy found no or only moderate reductions in the relative risk of developing pre-eclampsia. Low-dose aspirin was possibly started too late, that is after the first episode of trophoblast invasion. STUDY DESIGN, SIZE, DURATION: We performed a meta-analysis with individual patient data (IPD), in which four authors could provide IPD on a total of 268 pregnancies (n = 131 treated with aspirin, n = 137 placebo). Data on hypertensive pregnancy complications and preterm delivery were collected. PARTICIPANTS/MATERIALS, SETTING, METHODS: All separate databases were merged into a summary database. Treatment effect of aspirin on the incidence of hypertensive pregnancy complications (n = 187) and preterm delivery (n = 180) were estimated with odds ratios (OR) and 95% confidence intervals (95% CI) using multivariable logistic regression. MAIN RESULTS AND THE ROLE OF CHANCE: There were significantly fewer twin pregnancies in the aspirin group (OR 0.55 95% CI 0.30-0.98), but no significant differences for hypertensive pregnancy complications and preterm delivery: for singletons OR 0.62 (95% CI 0.22-1.7) and OR 0.52 (95% CI 0.16-1.7), respectively, as well as for twin pregnancies OR 1.2 (95% CI 0.35-4.4) and OR 1.6 (95% CI 0.51-5.0), respectively. LIMITATIONS, REASONS FOR CAUTION: We have to bear in mind that the included studies showed clinical heterogeneity; there was variation in the duration of low-dose aspirin therapy and degree of hypertension between the different studies. Although we combined IPD from four studies, we have to realize that the studies were not powered for the outcome of the current IPD meta-analysis. WIDER IMPLICATIONS OF THE FINDINGS: Based on the current meta-analysis with IPD we found no confirmation for the hypothesis that preconceptionally started low-dose aspirin reduces the incidence of hypertensive pregnancy complications or preterm delivery in IVF women. Larger studies are warranted.

Factors associated with dizygotic twinning after IVF treatment with double embryo transfer.

BACKGROUND: Dizygotic twin pregnancies after IVF treatment are the result of multiple embryos transferred into the uterine cavity, followed by successful double implantation. Factors that increase the chance of multiple implantation after IVF are relatively unknown. The present study aimed to investigate whether features of body composition, such as maternal height, weight and body mass index (BMI) are associated with an increased chance of dizygotic twinning after IVF with double embryo transfer (DET). METHODS: This study was conducted using data from a large Dutch nationwide cohort that comprised 19 861 women who had IVF or ICSI treatment between 1983 and 1995 (OMEGA study). First 'fresh' IVF and ICSI cycles with DET resulting in a delivery of a singleton or twin (living as well as stillborn) were selected. A multivariable logistic regression analysis was performed, with the delivery of a singleton or twin as the dependent variable and height, weight, BMI, maternal age, number of retrieved oocytes, use of alcohol, smoking, highest level of education and parity as independent variables. RESULTS: Of the 6598 women who completed their first IVF or ICSI cycle, 2375 had DET, resulting in 496 deliveries of 371 singletons and 125 twins. Multivariable regression analysis revealed that tall women (>1.74 cm) and women with a high number of retrieved oocytes (>8) had an increased chance of dizygotic twinning [OR: 1.8 (95% CI: 1.0-3.4) and OR: 2.2 (95% CI: 1.3-3.8), respectively]. CONCLUSIONS: Our data demonstrate that tall stature and increased number of retrieved oocytes independently increase the chance of dizygotic twinning after IVF with DET.

Standardization of catheter load speed during embryo transfer: comparison of manual and pump-regulated embryo transfer.

The position of transfer air bubbles after embryo transfer is related to the pregnancy rate. With the conventional manual embryo-transfer technique it is not possible to predict the final position of the air bubbles. This position mainly depends on the catheter load speed at transfer (injection speed), a parameter that remains uncontrollable with the conventional technique even after standardization of the protocol. Therefore, the development of an automated device that generates a standardized injection speed is desirable. This study aimed to examine the variation in injection speeds in manual embryo transfer and pump-regulated embryo transfer (PRET). Seven laboratory technicians were asked to perform simulated transfers using the conventional embryo-transfer technique. Their injection speeds were compared with that of a PRET device. The results indicate that in manually performed transfers, even after standardization of the protocol, there is still a large variation in injection speed, while a PRET device generates a reliable and reproducible injection speed and therefore brings new possibilities for further standardization of the embryo-transfer procedure. Future research should reveal whether these experiments mimic real clinical circumstances and if a standardized injection speed results in more exact positioning of the transferred embryos and therefore higher pregnancy rates.

Is aspirin effective in women undergoing in vitro fertilization (IVF)? Results from an individual patient data meta-analysis (IPD MA).

BACKGROUND: Aspirin is believed to improve the outcome of IVF, but previous conventional meta-analyses on the subject are conflicting. Therefore, we performed a meta-analysis with individual patient data (IPD MA) of randomized clinical trials (RCTs) on the subject. METHODS: A systematic literature search was conducted to identify RCTs assessing the effectiveness of aspirin in IVF. Authors were asked to share their original data. In a one step meta-analytic approach, the treatment effect of aspirin was estimated with odds ratios (ORs) and 95% confidence intervals (CIs) using logistic regression, based on the intention to treat principle. RESULTS: Ten studies fulfilled the inclusion criteria. Authors of six studies provided IPD, including 1119 patients (562 placebo and 557 aspirin). There were 160 clinical pregnancies in the aspirin (28.8%) and 179 (31.9%) in the placebo group [OR 0.86, 95% CI (0.69-1.1)]. There were 129 ongoing pregnancies in the aspirin (23.6%) and 147 in the placebo group (26.7%) [OR 0.85, 95% CI (0.65-1.1)]. Whereas the conventional meta-analysis limited to studies that could provide IPD showed an OR of 0.89 (95% CI 0.69-1.2), the conventional meta-analysis limited to the eight studies of which method of randomization could be confirmed showed an OR of 0.94 (95% CI 0.76-1.17) and the conventional meta-analysis including all 10 eligible RCTs identified with our search changed the OR to 1.07 (95% CI 0.81-1.41). This difference in direction of effect, derived from the studies not able to share IPD of which quality of randomization could not be confirmed. CONCLUSIONS: Aspirin does not improve pregnancy rates after IVF.

A family history of twinning in relation to multiple implantation.

BACKGROUND: A familial basis for dizygotic twinning is known for multiple ovulation. However, for multiple implantation this remains unclear. In IVF/intracytoplasmic sperm injection (ICSI) 'multiple ovulation' is artificially induced. If multiple implantation is not hereditary, the incidences of twins in families of patients with single and multiple implantation after IVF/ICSI with double embryo transfer (DET) should be comparable. METHODS: A questionnaire study was conducted among patients with intra uterine pregnancy at 6 weeks of gestation, after IVF/ICSI treatment with DET 3 days after oocyte retrieval. RESULTS: There were 940 patients who gave their informed consent. For women with single implantation (Group A), the incidence of one and of multiple twins among the family was 27.2 and 15.5%, respectively. For women with multiple implantation (Group B), this incidence was 29.5 and 17.8%, respectively, P = 0.424. The incidence of one and of multiple twins among first degree relatives was 10.6 and 1.1% in Group A; for Group B this was 8.7 and 1.9%, P = 0.469. Multivariate regression analysis also did not reveal 'twins in family' or 'twins in first degree' as an associated variable for multiple implantation at 6 weeks. CONCLUSIONS: Incidences of twins in families of patients with single implantation and patients with multiple implantation after IVF/ICSI are comparable. Our data do not support the concept that multiple implantation is hereditary.

Factors determining early pregnancy loss in singleton and multiple implantations.

BACKGROUND: The incidence of first trimester pregnancy loss is much lower in IVF twin pregnancies than in IVF singleton pregnancies. The objective of this study was to determine which embryonic and maternal factors contribute to this finding. METHODS: Retrospective data analysis of the outcome of 1593 pregnancies after day 3 double-embryo transfer (DET) after IVF or ICSI treatment. RESULTS: Of 1148 single implantations at 6 weeks, 936 (81.5%) were ongoing pregnancies. Of 445 multiple implantations at 6 weeks, 354 (79.6%) were ongoing multiple pregnancies, 80 (17.9%) were ongoing singleton pregnancies and 11 (2.5%) ended in a spontaneous abortion. Total pregnancy loss was 18.5 and 2.5% (P < 0.001) in singleton and twin gestations, respectively. Loss per gestational sac was 18.5 and 11.46% (P < 0.001), respectively. Determinants contributing to the continuation of gestation beyond 6 weeks were young maternal age, possibility to cryopreserve embryos and short GnRH agonist flare-up stimulation protocol. Whereas factors promoting multiple implantation at 6 weeks of gestation were young maternal age, high cumulative embryo score (CES), male infertility, long stimulation protocol and thick endometrium. CONCLUSIONS: Although multiple implantation at 6 weeks is predominantly determined by (morphological) embryo quality, the continuation of pregnancy beyond 6 weeks becomes more dependent on the combination of genetic and developmental potential of the embryo(s) and an optimal uterine milieu.